Before computers, numerical analyses, particularly financial ones, were usually prepared on an accountant's columnar pad or spreadsheet, with pencil and calculator in hand. By organising data into columns and rows, spreadsheets afford the rapid assimilation of information by a reader. The task of preparing a spreadsheet on paper, however, is not quite so fast. Instead, the process tends to be very slow, as each entry must be tediously calculated and entered into the spreadsheet. Since all calculations are the responsibility of the preparer, manually prepared spreadsheets are also prone to errors. Hence, preparation of spreadsheets by hand is slow, tedious, and unreliable.
With the advent of microcomputers, a solution was forthcoming in the form of “electronic spreadsheets.” Better known simply as “spreadsheets,” these software programs provide a computerised replacement for the traditional financial modelling tools: the accountant's columnar pad, pencil, and calculator. In some regards, spreadsheet programs are to those tools what word processors are to typewriters. Spreadsheets offer dramatic improvements in ease of creating, editing, and using financial models.
A typical spreadsheet program configures the memory of a computer to resemble the column/row or grid format of an accountant's columnar pad, thus providing a visible calculator for a user. Because this “pad” exists dynamically in the computer's memory, however, it differs from paper pads in several important ways. Locations in the electronic spreadsheet, for example, must be communicated to the computer in a format which it can understand. A common scheme for accomplishing this is to assign a number to each row in a spreadsheet, a letter to each column, and another letter to each sheet (or page) of the spreadsheet. To reference a location at column A and row 1 of the second page (i.e., the upper-left hand corner), for example, the user types in “B:A1”. In this manner, the spreadsheet defines an addressable storage location or “cell” at each intersection of a row with a column within a given page.
Data entry into an electronic spreadsheet occurs in much the same manner that information would be entered on an accountant's pad. After a screen cursor is positioned at a desired location, the user can enter alphanumeric information. Besides holding text and numeric information, however, spreadsheet cells can store special instructions or “formulas” specifying calculations to be performed on the numbers stored in spreadsheet cells. Such spreadsheet cells can also be defined and named as a range as long as they are arranged as a convex set of cells. A typical example of such a named range simply corresponds to a regular table found in an accountant's pad. In this fashion, range names can serve as variables in an equation, thereby allowing precise mathematical relationships to be defined between cells. The structure and operation of a spreadsheet program, including advanced functions such as functions and macros, are documented in the technical, trade, and patent literature. For an overview, see e.g., Cobb, S., Using Quattro Pro 2,Borland-OsbomeIMcCraw-Mll, 1990; and LeBlond, G. and Cobb, D.,
Using 1-2-3, Que corp., 1985. The disclosures of each of the foregoing are hereby incorporated by reference.
Electronic spreadsheets offer many advantages over their paper counterparts. For one, electronic spreadsheets are much larger (i.e., hold more information) than their paper counterparts; electronic spreadsheets having thousands or even millions of cells are not uncommon. Spreadsheet programs also allow users to perform “what-if” scenarios. After a set of computational relationships has been entered into the worksheet, thanks to imbedded formulas for instance, the information can be recalculated using different sets of assumptions. The results of each recalculation appears almost instantaneously. Performing this operation manually, with paper and pencil, would require the recalculation of every relationship in the model for each change made. Electronic spreadsheet systems have been invented to solve these “what-if” problems: changing an input and seeing what happens to an output.
“What-if” problems can be formally represented by the definition of one or several user-defined options, each of them representing an assumption which can either be set as “True” or “False.” The effect of a single given user defined option can take different forms and requires that the spreadsheet user formally represent this effect thanks to different spreadsheet built-in means. With the spreadsheet technologies currently used, such spreadsheet means can be based on the writing of some spreadsheet formulas (requiring thus some in-depth knowledge of the formula language and syntax), or can also be based on the utilization of so-called “versions”. In both cases, there are several limitations which can turn these spreadsheet means into inefficient and error-prone solutions.
When relying on spreadsheet formulas, the user needs first to master the spreadsheet formula language, something which is by far not an easy task for somebody not used to programming languages. Then the user must define by himself some formal representation of the user-defined options, with the associated means for managing them: this second task is even more difficult as the user cannot rely on any stringent set of rules (as the ones implemented in a language compiler or interpreter) to determine if his work is error-free. Furthermore an electronic spreadsheet prepared by a given user with his or her own way of representing options will be difficult to be used by another user if the latter has not received precise instructions from the former on the way to handle the options. In short, unless mastering advanced programming skills, it is virtually impossible for a regular spreadsheet user to realise and share error-free “what-if” scenario thanks to user-defined options, by solely relying on the spreadsheet built-in formula language.
Current spreadsheet tools implement today the concept of versions and version groups, which represent some advantages with respect to the previous approach. Nevertheless using versions presents also some limitations, as outlined hereafter. With conventional electronic spreadsheets, versions are associated to ranges of cells. Once a range of cell is “versionned”, the user can defined several versions for this range. In the classical case where multiple options must be managed, the number of versions to be defined may become excessive. Indeed if an electronic spreadsheet must address a set of N independent options, any cell whose content depends on these N options should be represented with 2Nversions, each of them corresponding to a given combination of these N options. Besides the resulting increase in file and memory storage (leading to degraded performances), this situation may become almost unmanageable for the user, specially in the case where multiple dispersed cells are versionned, even with the concept of version groups allowing to associate versions on different ranges of cells.